CN113114318B - Novel millimeter wave multi-user beam alignment method - Google Patents
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- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
- H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
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- H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
- H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
- H04B7/0617—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal for beam forming
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- H04B7/0837—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the receiving station using pre-detection combining
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Abstract
The invention belongs to the technical field of communication, and particularly relates to a beam alignment scheme based on a dilution coding theory in a millimeter wave multi-user scene. The invention firstly converts the uplink multi-user beam alignment problem into a dilution coding and decoding problem through the reasonable design of the transmitting beam and the receiving beam, and simultaneously decomposes the measurement matrix into two parts, namely a dilution coding matrix and a detection matrix. Then, a dilution detection matrix, and a detection method are proposed based on the received coding matrix of the dilution coding.
Description
Technical Field
The invention belongs to the technical field of communication, and particularly relates to a wave beam alignment method based on a sparse coding theory in a millimeter wave multi-user scene.
Background
Driven by technologies such as ultra-high-definition video, intelligent vehicle-mounted communication and virtual reality, the capacity of a global mobile system will increase sharply in the coming years. Whereas millimeter wave technology may utilize greater communication bandwidth and rate for communication. However, transmission in the millimeter wave band has a higher path loss than that in the low frequency band. Whereas large-scale antenna arrays may compensate for energy attenuation of the signal by beamforming. Challenges are presented to the design of massive MIMO channel estimation algorithms operating in millimeter wave environments.
In recent years, we estimate the channel using methods based on CS or CP decomposition by exploiting the sparsity of the mmwave MIMO channel. However, these algorithms have high computational complexity due to the large matrix operation. To reduce computational complexity, the academia has studied a series of beam scanning and search algorithms. Clearly, the simplest and intuitive beam search method is to search all candidate beams exhaustively, but it has a high sampling complexity. To solve this problem, some literature adaptive algorithms propose a method for reducing pilot overhead based on a hierarchical beam scanning codebook, but require a feedback link. Specifically, some documents implement the cancellation of the feedback link by using Pseudo-Random Spreading Codes (PRSC), but it needs a Pseudo-Noise sequence (PN) sufficiently long to ensure the independence of different beams. Therefore, there is an urgent need to design a new millimeter wave beam alignment scheme to reduce pilot sequences while maintaining good performance.
Disclosure of Invention
The invention aims to design a novel beam alignment scheme based on a sparse coding theory to be applied to a millimeter wave multi-user scene. The invention firstly converts the uplink multi-user beam alignment problem into a dilution coding and decoding problem through the reasonable design of the transmitting beam and the receiving beam, and simultaneously decomposes the measurement matrix into two parts, namely a dilution coding matrix and a detection matrix. Then, a dilution detection matrix, and a detection method are proposed based on the received coding matrix of the dilution coding.
The core idea of the invention is to realize millimeter wave multi-user uplink beam alignment by using a dilution coding structure.
To effectively explain the algorithm structure to be studied in this section, first consider a typical mm-wave Multi-User Multiple Input Multiple Output (MU-MIMO) system, as shown in fig. 1, in which a Base Station (BS) communicates with K users simultaneously. Suppose that the BS side is equipped with NRA receiving antenna and NRFA radio frequency link (N)RF<NR) And the kth User (User, UE) is equipped with MTAn antenna and MRFA radio frequency link. In order to realize spatial multiplexing under the conditions of low complexity and low power consumption, a hybrid precoding architecture is used by the BS and the UE. Thus, the millimeter wave uplink multi-user channel of the transmitting and receiving end can be expressed as follows
WhereinAOA, AOD, and channel complex gain of the ith path, respectively, representing the kth user. Also, due to the unique properties of the millimeter wave channel, the complex gain of the millimeter wave channel may be modeled as a rice fading profile as follows
WhereinIntegral complex gain amplitude of the channel, ηl,kRepresents the ratio of LOS path components to NLOS path components, andrepresenting a complex gaussian random variable. In addition, the ULA is used at the transceiving end, so that the vector is pointed toAndare respectively represented as
Where λ denotes the wavelength, where d is set to λ/2.
Again for an abstract understanding of our algorithmic logic,we are illustrated in figure 2. The measurement matrix is sparse, non-zero beam indexes are estimated through the sparse measurement matrix, and a problem with sparsity of 3 is converted into a problem with sparsity of 1 and sparsity of 2 through the sparse measurement matrix. The invention has more involved concepts and simply lists and dilutes the coding matrixThe relationship with the actual transmit beam is shown in figure 3. Meanwhile, according to the multipath distribution of the millimeter wave channel and the degree distribution of the received pins, the following types can be defined
(1) And (4) zero pin: define a right node as zero pin when it is not connected to the virtual angle domain channelIs a non-zero element of (c).
(2) Single pin: defining a right node as a single pin as it has and communicates only with the angular domainOne non-zero element is connected.
(3) Multiple pins: defining a right node as a multi-pin channel with angle domainA plurality of non-zero elements are connected.
The invention provides a sparse coding-based beam alignment method, which comprises the following steps:
WhereinAnd K represents the RF precoding matrix, the digital precoding matrix and the number of the UE in the uplink channel respectively. N (t) to CN (0,1) represent additive noise vectors of Gaussian distribution.
The receiver processes each RF link individually at a time, and the data at the receiver is represented here for simplicity as
WhereinIs a beam space representation method in whichAndto represent the DFT matrix, the DFT matrix is shown,represents a virtual angular domain index, andindicating selectionOne line of (1), fkAnd (t) is a transmission vector of k users.For the BS side, the receive side beam space is periodically scanned by simultaneously forming multiple beams.
In the following description, we simplify riR for the following description.
ψ=G⊙S
Wherein |, indicates a line tensor operation. Mathematically, the measurement matrix psi can be re-expressed as
Wherein G isiAnd SiRespectively represent the ith columns of matrix G and matrix S, anRepresenting the Kronecker product.
TABLE 1 parameter μ selection and corresponding layer number d
|
3 | 4 | 5 | 6 | 7 | 8 |
μ | 1.221 | 1.292 | 1.425 | 1.566 | 1.715 | 1.864 |
The encoding matrix is then designed such that each phase possesses a cyclically shifted sub-sampling pattern. When the diluting coding matrix is specifically designed, the number of layers and the number of rows which meet the requirements of the bipartite graph are designed, then the non-zero values in each row are translated in a randomized circulation mode, and the non-zero values appear in each node in a circulation mode for sampling.
Step 6, aiming at the noise scene, designing a diluted detection matrixThe columns in which each stage has a value can be represented asWherein M isiIs the number of non-zero elements in the matrix G in each layer. In particular, to effectively combat the effects of noise, the matrix DiThe medium element is a random gaussian variable and remains constant modulo. In order to effectively explain the coding structure, as shown in fig. 4, the relationship between the measurement matrix and the sparse coding matrix is shown; and transmitting beams through the constructed sparse coding matrix and the sparse detection matrix.
Step 7, detecting whether the receiving vector is zero or not as follows
WhereinWhich is indicative of the minimum signal power,is the minimum noise power, ε1Is zero pin detection threshold, ri,j[1]And correspondingly diluting the received first numerical value of the jth pin vector in the ith stage and the jth pin vector sent in the encoding matrix.
Step 8, if the received vector is not zero-pin, then the received pin vector is assumed to be single-pin and the beam index pair thereof is estimated at the same timeSpecifically, for the ith pin of each layer, the most likely coefficient is obtained using a Maximum Likelihood (ML) algorithm as follows
Step 9, using known checking steps to decide whether the received vector is a single pin, and the following decision criteria are used as follows
WhereinWhich is indicative of the minimum signal power,is the minimum noise power, ε2Is a single pin detection threshold.
The invention is mainly applied to a millimeter wave multi-antenna communication system, and has the advantages that:
1) compared with the traditional CS-based channel estimation algorithm, the proposed uplink multi-user estimation method has shorter operation calculation time and obtains similar performance to the traditional method under the condition of correspondingly improving the pilot frequency overhead.
2) Compared with the latest beam alignment algorithm, the detection probability under the same measurement overhead is improved by the algorithm.
Drawings
FIG. 1 is a schematic diagram of a millimeter wave Massive MIMO communication system according to the present invention;
FIG. 2 is a logic diagram of millimeter wave diluting encoding beam alignment algorithm in the algorithm
FIG. 3 is a schematic diagram of the relationship between the sparse coding matrix and the transmit beam in the present invention;
fig. 4 is a regular bipartite graph corresponding to a sparse coding matrix in the present invention, where the right degree is b-2;
FIG. 5 shows that the detection probability of the proposed algorithm and the latest random search algorithm under different measurement overheads in a noisy sceneBy contrast, where SNR is 5dB, and N of the random search algorithmc=32。
Fig. 6 shows the comparison between the proposed algorithm and the distribution lattice point matching algorithm under different SNR conditions in the noise scene and under the alignment condition according to the present invention, and the measurement overhead of the two algorithms is 256 and 96 respectively.
Detailed Description
The technical scheme of the invention is described in detail in the following by combining the attached drawings and examples.
Examples
In this example, the number of users is set to K16, the BS terminal uses a unit line array, and N is the numberR64 and NRFThe UE uses a unit line array, M, 16T16 and M RF4. Meanwhile, assume that the number of multipaths of different users is L k4 and K factor in the channel is Kfactor=20dB。
The example includes the following steps
Step 1: the BS end utilizes a plurality of RF links to simultaneously form a plurality of beams, the receiving end traverses and searches each possible path at each sending moment, and simultaneously the receiving end separates data received by different beams to be respectively processed.
Step 2: transmitting end constructing sparse coding matrixThe bipartite graph whose design criteria derive from the use of the algorithm is a rule bipartite graphDerived from the collection. In this set, the m-th detection node is divided into d stages, where each left node is randomly connected to one right node at each stage. We define the set F ═ { F1…fdRepresents the number of right nodes at the stage i as fi. And, for all i and random redundancy parameters μ, fiμ K + o (1). Wherein the parameters μ are selected and the corresponding number of layers d is shown in Table 1 below
TABLE 1 parameter μ selection and corresponding layer number d
|
3 | 4 | 5 | 6 | 7 | 8 |
μ | 1.221 | 1.292 | 1.425 | 1.566 | 1.715 | 1.864 |
The coding matrix is then designed based on the bipartite graph so that each phase has a cyclically shifted sub-sampling pattern.
And step 3: multiple user transmitting end joint transmitting beam, its joint dilution coding matrixConstructing a sparse detection matrix, wherein a diluted detection matrix is designedThe columns in which each stage has a value can be represented asWherein M isiIs the number of non-zero elements in the matrix G in each layer. In particular, to effectively combat the effects of noise, the matrix DiThe medium element is a random gaussian variable and remains constant modulo. In order to effectively explain the coding structure, as shown in fig. 3, the relationship between the measurement matrix and the sparse coding matrix is shown.
And 4, step 4: the beam is transmitted one by one according to logic similar to that in figure 3 through the constructed sparse coding matrix and the sparse detection matrix.
And 5: the detection of whether the received vector is zero or not is as follows
WhereinWhich is indicative of the minimum signal power,is the minimum noise power, ε1Is zero pin detection threshold, ri,j[1]And correspondingly diluting the received first numerical value of the jth pin vector in the ith stage and the jth pin vector sent in the encoding matrix.
Step 6: if the received vector is not a zero-pin, then the received pin vector is assumed to be a single pin while estimating its beam index pairSpecifically, for the ith pin of each layer, the most likely coefficient is obtained using a Maximum Likelihood (ML) algorithm as follows
And 7: the decision whether a received vector is a single-pin is determined using known checking steps, with the following decision criteria
WhereinWhich is indicative of the minimum signal power,is the minimum noise power, ε2Is a single pin detection threshold.
And 8: if the received vector is detected as a single pin, thenThe process of multiple iteration can be artificially set for L times of iteration, and meanwhile, when a single pin of the UE user number is found, the iteration is stopped. Finally, the estimated mappingTo the actual beam index
In summary, the present invention provides a novel millimeter wave multi-user beam alignment scheme, which can be applied to uplink multi-user beam alignment of an actual millimeter wave multi-antenna system. The scheme researches a wave beam alignment algorithm framework based on sparse coding, provides a novel sparse coding and decoding method aiming at a noise scene, and is based on the wave beam alignment framework, the performance is superior to the latest wave beam alignment algorithm, and the estimation channel performance approaches to the traditional algorithm based on compressed sensing under the full alignment condition.
Claims (1)
1. A novel millimeter wave multi-user beam alignment method, in a millimeter wave multi-user system, comprises a base station BS and K user UEs, wherein the BS end is provided with NRA receiving antenna and NRFA radio frequency link, NRF<NRAnd the kth UE is equipped with MTAn antenna and MRFA radio frequency link, wherein the beam alignment method comprises the steps of:
s1, the BS end receives a plurality of UE transmitting beams simultaneously and passes through an RF integration matrixAnd a digital integration matrixThe locally customized beamforming codebook W (t) ═ WRF(t)WBB(t)=FBSv (t), where v (t) represents an index matrix of quantization angles, where the non-zero values are 1, FBSRepresenting a DFT matrix; the BS side receives data by using different RF links, and the receiving side signals are represented as:
whereinAnd K respectively represents the RF precoding matrix, the digital precoding matrix and the number of UE in the uplink channel,is a beam space representation method in whichAnddenotes a DFT matrix, s (t) is a transmission signal, N (t) -CN (0,1) denotes an additive noise vector of Gaussian distribution;
each RF link is processed individually by the receiving end at a time, and the data at the receiving end is represented as:
wherein the content of the first and second substances,indicating selectionOne of the rows in the group (a),representing a virtual angular domain index, fk(t) for the transmission vectors of k users, for the BS, periodically scanning the receiving end beam space by simultaneously forming a plurality of beams;
s2, UE transmits a plurality of wave beams simultaneously, and the transmission vector is fk(t)=FRF,k(t)FBB,k(t)=FMSψk(t) in whichCoding matrix for representing k-th user, and reducing received data to riR, expressed as:
S3, collecting data at time T:
s4, defining T as MN, designing a measurement matrixDivide it into two parts, including sparse coding matrixAnd a detection matrixThe measurement matrix psi is:
ψ=G⊙S
wherein |, indicates a line tensor operation, re-indicating the measurement matrix ψ as:
wherein G isiAnd SiRespectively represent the ith columns of matrix G and matrix S, anRepresents the Kronecker product;
s5, constructing a sparse coding matrixSuppose a bipartite graphIn the set, the m-th detection node is divided into d stages, wherein each left node is randomly connected with one in each stageA right node, defining a set F ═ F1…fdRepresents the number of right nodes at the stage i as fiAnd, for all i and random redundancy parameters μ, fiμ K + o (1); constructing a sparse coding matrix based on a bipartite graph, so that each phase has a circularly translated sub-sampling graph;
s6, aiming at noise scenes, designing a sparse detection matrixWherein each phase has a column of values represented asWherein M isiThe number of non-zero elements in the matrix G in each layer is counted; matrix DiThe medium element is a random gaussian variable and remains constant modulus; transmitting beams through the constructed sparse coding matrix and the constructed sparse detection matrix;
s7, detecting whether the received vector is a zero pin, wherein the definition of the zero pin is that when a right node is not connected to the virtual angle domain channelIs a zero pin:
whereinWhich is indicative of the minimum signal power,is the minimum noise power, ε1Is zero pin detection threshold, ri,j[1]Correspondingly diluting a received first numerical value of a j pin vector at the ith stage in the coding matrix;
s8, if yesIf the received vector is not zero-lead, then the received lead vector is assumed to be single-lead and its beam index pair is estimated simultaneouslyThe definition of single pin is that when a right node has and only communicates with the angle domainWhen one non-zero element is connected, the non-zero element is a single pin, and for the ith pin of each layer, the most possible coefficients are obtained by using a maximum likelihood algorithm as follows:
S9, using known checking steps to decide whether the received vector is a single pin, the following decision criteria are used:
whereinWhich is indicative of the minimum signal power,is the minimum noise power, ε2Detecting a threshold for a single pin;
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